Confronting the US's Highly Uneven State-by-State Distribution of Diagnostic Radiology Residency Positions

The state-by-state distribution of diagnostic radiology residency positions is important for several reasons. The location in which residents train is positively correlated with their eventual practice location, and states with relatively few residents may have greater difficulty meeting needs for radiology services ( 1 ). The presence of residents can also enrich the educational experiences of other learners such as medical students, but this is less likely to happen when residents are in short supply ( 2 ). Finally, because residency training programs can promote a culture of inquiry, a dearth of residents may undermine intellectual engagement within a professional community ( 3 )

Contrast Leakage Patterns from Dynamic Susceptibility Contrast Perfusion MRI in the Grading of Primary Pediatric Brain Tumors

BACKGROUND AND PURPOSE: The pattern of contrast leakage from DSC tissue signal intensity time curves have shown utility in distinguishing adult brain neoplasms, but has limited description in the literature for pediatric brain tumors. The purpose of this study is to evaluate the utility of grading pediatric brain tumors with this technique. MATERIALS AND METHODS: A retrospective review of tissue signal-intensity time curves from 63 pediatric brain tumors with preoperative DSC perfusion MR imaging was performed independently by 2 neuroradiologists. Tissue signal-intensity time curves were generated from ROIs placed in the highest perceived tumor relative CBV. The postbolus portion of the curve was independently classified as returning to baseline, continuing above baseline (T1-dominant contrast leakage), or failing to return to baseline (T2*-dominant contrast leakage). Interobserver agreement of curve classification was evaluated by using the Cohen κ. A consensus classification of curve type was obtained in discrepant cases, and the consensus classification was compared with tumor histology and World Health Organization grade. RESULTS: Tissue signal-intensity time curve classification concordance was 0.69 (95% CI, 0.54–0.84) overall and 0.79 (95% CI, 0.59–0.91) for a T1-dominant contrast leakage pattern. Twenty-five of 25 tumors with consensus T1-dominant contrast leakage were low-grade (positive predictive value, 1.0; 95% CI, 0.83–1.00). By comparison, tumors with consensus T2*-dominant contrast leakage or return to baseline were predominantly high-grade (10/15 and 15/23, respectively) with a high negative predictive value (1.0; 95% CI, 0.83–1.0). For pilomyxoid or pilocytic astrocytomas, a T1-dominant leak demonstrated high sensitivity (0.91; 95% CI, 0.70–0.98) and specificity (0.90, 95% CI, 0.75–0.97). CONCLUSIONS: There was good interobserver agreement in the classification of DSC perfusion tissue signal-intensity time curves for pediatric brain tumors, particularly for T1-dominant leakage. Among patients with pediatric brain tumors, a T1-dominant leakage pattern is highly specific for a low-grade tumor and demonstrates high sensitivity and specificity for pilocytic or pilomyxoid astrocytomas

Revision of Oxandra (Annonaceae)

A taxonomic revision is given of the Neotropical genus Oxandra (Annonaceae). Within the genus 27 species are recognized, 4 of which are new to science. Most of the species are occurring in tropical South America, whereas a few (6) are found in Mexico and Central America and two in the West Indies (Greater and Lesser Antilles). A key to all species is provided. The treatment includes chapters about the history of the genus and morphology. All species are fully described, including full synonymy, notes on distribution and ecology, field observations (when available), vernacular names (when given), and mostly short notes about relationships of the species concerned. For each species a distribution map is made. At the end of the revision a complete list of vernacular names is included.Peer reviewe

Multi-nuclear, high-pressure, operando FlowNMR spectroscopic study of Rh/PPh3 – catalysed hydroformylation of 1-hexene

The hydroformylation of 1-hexene with 12 bar of 1 : 1 H2/CO in the presence of the catalytic system [Rh(acac)(CO)2]/PPh3 was successfully studied by real-time multinuclear high-resolution FlowNMR spectroscopy at 50 °C. Quantitative reaction progress curves that yield rates as well as chemo- and regioselectivities have been obtained with varying P/Rh loadings. Dissolved H2 can be monitored in solution to ensure true operando conditions without gas limitation. 31P{1H} and selective excitation 1H pulse sequences have been periodically interleaved with 1H FlowNMR measurements to detect Rh–phosphine intermediates during the catalysis. Stopped-flow experiments in combination with diffusion measurements and 2D heteronuclear correlation experiments showed the known tris-phosphine complex [RhH(CO)(PPh3)3] to generate rapidly exchanging isomers of the bis-phosphine complex [Rh(CO)2(PPh3)2] under CO pressure that directly enter the catalytic cycle. A new mono-phosphine acyl complex has been identified as an in-cycle reaction intermediate

Artificial Metalloenzymes as Catalysts for Oxidative Lignin Degradation

We report novel artificial metalloenzymes (ArMs), containing tris­(pyridylmethyl)­amine (TPA), for the atom economic oxidation of lignin β-O-4 model compounds, using hydrogen peroxide. The protein scaffold alters the selectivity of the reaction from a low yielding cleavage reaction when using the parent Fe-tpa complex to a high yielding benzylic alcohol oxidation when using the complex incorporated into a protein scaffold, SCP-2L A100C. Engineering the protein scaffold to incorporate glutamic acid was found to improve the ArM activity, showing that rational design of the protein environment using metal binding amino acids can be a first step toward improving the overall activity of an artificial metalloenzyme

UTICAJ BAKTERIJSKE KONTAMINACIJE STOČNE HRANE NA ZDRAVLJE ŽIVOTINJA

The authors thank the European Union (Marie Curie ITN SusPhos, grant agreement no. 317404) for financial support.An efficient modular method towards the synthesis of a library of polystyrene supported diphosphine ligands by combining solid-phase synthesis with rational ligand design has been developed. These supported ligands, obtained in quantitative yield, were efficiently and effectively screened in Rh-catalysed asymmetric hydrogenation of several benchmark substrates.Publisher PDFPeer reviewe